1. Field
The present invention relates to formation (e.g., deposition) of films in devices such as semiconductor and integrated circuit devices, and, more particularly, to diffusion barrier films in semiconductor devices.
2. Description of the Related Art
The semiconductor industry is constantly searching for ways to increase the speed of integrated circuits. For example, faster interconnect technology such as copper interconnects provide an improvement over older technologies since copper provides a faster signal medium.
In integrated circuits, a dielectric layer is used to provide insulation around the interconnect wiring of the chip. Just as faster interconnect materials such as copper allow a signal to move faster through the chip, decreasing the capacitance factor of the insulating material also allows signals to travel across the interconnect faster because they have less interference with each other. The most common dielectric material is silicon dioxide. However, the semiconductor industry is constantly searching for commercially useful, lower capacitance dielectric materials, commonly referred to as low dielectric constant or low k materials.
Conventional cobalt (Co) films doped with elements like tungsten (W), molybdenum (Mo), rhenium (Re), etc. are reported to have barrier properties to prevent diffusion of copper into a surrounding dielectric material. This can enable integration of copper with low k materials. Also capping copper with these types of materials can enhance reliability by increasing electromigration resistance. In order to be successful a very selective deposition of these films is required.
Electroless deposition is one method for selective deposition. Many barrier formation techniques require catalytic activation which often has problems of selectivity due to a high probability of nucleation in non-metal area. Non-activation barrier deposition processes typically require operating temperatures which are relatively higher for conventional electroless methods, and such higher temperatures reduce the chemical stability of electroless plating baths. Since alkaline solutions are employed as plating baths, better compatibility with low k dielectric materials could be achieved at lower temperatures. Thus, there is a need for an efficient and effective means of capping copper interconnect structures with diffusion barrier material.